opencv create mat from camera data

in my programm I have function that takes the image from camera and should pack all data in OpenCV Mat structure. From the camera I get width, height and unsigned char* to the image buffer. My Question is how I can create Mat from this data, if I have global Mat variable. The type for Mat structure I took CV_8UC1.

Mat image_;

function takePhoto() {
    unsigned int width = getWidthOfPhoto();
    unsinged int height = getHeightOfPhoto();
    unsinged char* dataBuffer = getBufferOfPhoto();
    Mat image(Size(width, height), CV_8UC1, dataBuffer, Mat::AUTO_STEP);

    printf("width: %u\n", image.size().width);
    printf("height: %u\n", image.size().height);

    image_.create(Size(image.size().width, image.size().height), CV_8UC1);
    image_ = image.clone();

    printf("width: %u\n", image_.size().width);
    printf("height: %u\n", image_.size().height);
}

When I test my program, I get right width and height of image, but width and height of my global Mat image_ is 0. How I can put the data in my global Mat varible correctly?

Thank you.